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A Photometric Method for Quantifying Asymmetries in Disk Galaxies

David A. Kornreich·Martha P. Haynes·Richard V. E. Lovelace
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Abstract

A photometric method for quantifying deviations from axisymmetry in optical images of disk galaxies is applied to a sample of 32 face-on and nearly face-on spirals. The method involves comparing the relative fluxes contained within trapezoidal sectors arranged symmetrically about the galaxy center of light, excluding the bulge and/or barred regions. Such a method has several advantages over others, especially when quantifying asymmetry in flocculent galaxies. Specifically, the averaging of large regions improves the signal-to-noise in the measurements; the method is not strongly affected by the presence of spiral arms; and it identifies the kinds of asymmetry that are likely to be dynamically important. Application of this "method of sectors" to R-band images of 32 disk galaxies indicates that about 30% of spirals show deviations from axisymmetry at the 5-sigma level.

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David A. Kornreich, Martha P. Haynes, Richard V. E. Lovelace. 1998-07-29. A Photometric Method for Quantifying Asymmetries in Disk Galaxies. https://doi.org/10.1086/300598

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